Estimated Nest Success Research Articles

Variation in nest survival of three species of tropical plovers in Madagascar with clutch size, age of nest, year and El Niño effect.

A combination of life history traits and environmental conditions has been highlighted as the main drivers of avian breeding success. While drivers of breeding success are well known in some species, especially birds in northern, temperate regions; species in other parts of the world have received relatively little attention. In this study, we used a long-term dataset on breeding success of tropical plovers from south-west Madagascar to investigate whether nest survival changed over time and whether the drivers of nest survival were similar for multiple species breeding in the same arid habitat. In the 12-year period of 2009-2020, we monitored 2077 nests for three species with different breeding strategies: 1185 nests of Kittlitz's plovers (Anarhynchus pecuarius) with a flexible breeding strategy and uniparental care; and 565 nests of white-fronted plovers (A. marginatus) and 327 nests of Madagascar plovers (A. thoracicus) which both have biparental care. We found that nest survival was associated with a combination of clutch-size, age of nest and year among the three plover species. In addition, annual variation in climatic conditions associated with El Niño/La Niña events were included in the most supported survival models for Kittlitz's and white-fronted plovers, but the effects were not significant. Overall estimates of daily nest survival were similar for all three species: Kittlitz's plover: 0.950 ± 0.002 SE, Madagascar plover: 0.919 ± 0.007 SE, and white-fronted plover: 0.862 ± 0.047 SE. Estimates of nest success for the breeding season, based on increases in daily nest survival with the clutch age during the incubation periods (26 days for Kittlitz's plovers and 29 days for Madagascar and white-fronted plovers), were relatively low: Kittlitz's plover: 0.161 ± 0.056 SE, Madagascar plover: 0.287 ± 0.022 SE, and white-fronted plover: 0.228 ± 0.019 SE. All three species had a combination of factors affecting nest survival, both environmental and life history traits.

Evaluation of fall‐seeded cover crops for grassland nesting waterfowl in eastern South Dakota

AbstractThe Prairie Pothole Region (PPR) is the primary breeding ground for many species of North American waterfowl. The PPR was historically dominated by mixed and tallgrass prairies interspersed with wetlands, but >70% of the native grassland area has been lost due to widespread conversion to croplands. Cover cropping is a reemerging farming technique that may provide suitable nesting cover for grassland nesting waterfowl in active croplands, but waterfowl nest survival in fall cover‐cropped fields has not been evaluated. We studied use (nest abundance and density) and nest survival of breeding waterfowl in fall‐seeded cover crops and perennial cover during 2018 and 2019. We searched 2,094 ha of cover crops and 1,604 ha of perennial cover and found 123 and 304 duck nests, respectively, in each cover type. Estimated nest success (34‐day interval) was 3.7% and 16.6% in cover crops during 2018 and 2019, respectively, versus 22.1% in 2018 and 24.9% in 2019 in perennial cover, with increased success of cover‐crop fields in 2019 resulting from precipitation that prevented most fields from being planted to row crops. In a model that included effects of planting, daily nest survival in perennial cover was 0.944 (SD = 0.026) in 2018 and 0.960 (SD = 0.019) in 2019. Estimated daily nest survival was 0.912 (SD = 0.040) in 2018 and 0.960 (SD = 0.019) in 2019 during intervals when planting did not occur, but was only 0.417 (SD = 0.124) in 2018 and 0.612 (SD = 0.117) in 2019 on the day that planting occurred. Estimated nest densities in 2018 and 2019, adjusted for nests that failed prior to discovery, were 5.1 (SE = 1.1) and 11.0 (SE = 3.1) nests 100‐ha−1 in perennial cover, but only 2.1 (SE = 0.8) and 2.6 (SE = 0.7) in cover crops, respectively. Based on observed nest initiation and planting dates, about 70% of duck nests in cover crops would experience planting events in a typical growing season. Our results suggest that under current management techniques, fall‐seeded cover crops offer poor nesting habitat for waterfowl; however, the important benefits cover crops provide to soil health, water quality, and other ecosystem services remain.

Timing of breeding as a determinant of nest success of the vulnerable Chestnut Seedeater (Sporophila cinnamomea) in grasslands of southern South America

The breeding traits of Sporophila seedeaters have been relatively well studied in recent years; nevertheless, a group of ten species in the genus, known as southern capuchinos, remain understudied. That is the case with Chestnut Seedeater (Sporophila cinnamomea), a species vulnerable to extinction, which breeds in the grasslands of southeast South America and, after reproduction, migrates towards the Cerrado region in central Brazil. Here, we investigated breeding ecology and calculated average clutch size, productivity, the sex ratio of nestlings, and estimated nest success. Then we tested (1) whether there is a relationship between the number of active nests and environmental variables, (2) whether the nestling sex ratio deviates from the 1:1 ratio, (3) whether clutch size varies between breeding seasons, and (4) whether the nest success is related to starting date, nest age, plant support, nest height from the ground, and clutch size. During two breeding seasons (October–March 2018–2020), we monitored 98 nests. We generated survival models with five interacting covariates to assess the survival of the nests. We recorded the entire breeding period for Chestnut Seedeater, which was estimated to be 4.6 months, similar to other migratory seedeaters. Clutch size did not differ between breeding seasons. The sex ratio of nestlings was not significantly different from the 1:1 ratio. Nest success was 31%, and predation was the leading cause of unsuccessful nests (83%). The daily survival rate was 0.95 ​± ​0.01. The main predictor of nest survival was the covariate starting date. These findings, added to other aspects of the species' natural history described here, may help illuminate the ecology and behavior of Chestnut Seedeater and other southern endangered capuchinos, and grassland-dependent species of South America.

Breeding Ecology of Mottled Ducks: A Review

ABSTRACTMottled ducks (Anas fulvigula) are endemic to the Gulf Coast of North America, and their range stretches from Alabama to the Laguna Madre of Mexico, with a distinct population in peninsular Florida and an introduced population in South Carolina. As one of the few non‐migratory ducks in North America, mottled ducks depend on a variety of locally available habitat throughout the annual cycle, and threats to these landscapes may affect mottled ducks more acutely than migratory species. Annual population monitoring has revealed declines in mottled duck populations in Texas and Louisiana since 2008, and the genetic integrity of the Florida population has been muddled by the presence of large numbers of feral mallards (Anas platyrhynchos) resulting in hybridization. Similar to other closely related dabbling ducks, mottled duck populations are influenced by recruitment and breeding season survival, so changes in these factors may contribute to population decline. Accordingly, researchers have attempted to address various aspects of mottled duck breeding season ecology and population dynamics since the 1950s. We conducted a literature review on this topic by searching a combination of key terms using Google Scholar, including mottled duck, nesting ecology, habitat use, breeding incidence, nest success, brood, and breeding season survival, and followed citation trees to eventually aggregate information from nearly 50 publications on mottled duck breeding ecology. Our review concluded that mottled ducks use brackish and intermediate coastal marsh, including managed impoundments, and agricultural land during the breeding season. Their nests can be found in pastures, levees, dry cordgrass marsh, cutgrass marsh, spoil banks, and small islands. Nesting propensity and nest success estimates are often lower than other waterfowl species that are characterized by stable or increasing populations. Broods use wetlands composed of a mix of open water with submerged and emergent vegetation. Breeding season survival is higher for the Florida population than the western Gulf Coast population, but adult survival in both geographies is comparable to (or higher than) that of other dabbling duck species. Breeding habitat use, breeding season survival, and nest‐site selection and success have been studied extensively in mottled ducks, whereas information on nesting propensity, renesting intensity, and post‐hatch ecology is lacking. © 2021 The Wildlife Society.

Effects of Class-Level Vegetation Characteristics on Nesting Success of Bewick's Wrens

Understanding how habitat affects avian nest success is paramount, particularly when nest boxes are used. Once widespread, Thryomanes bewickii (Bewick's Wren) are presently confined to south-central and western North America. Our objective was to determine which vegetation variables influenced Bewick's Wren nesting success in nest boxes in central Texas. Between 2013 and 2014, we estimated nest success for 83 nests and measured vegetation variables surrounding nest boxes. Shrubland perimeter-area ratio negatively impacted nest success, whereas distance to nearest tree had a positive effect. Our results indicate that nests close to trees and in patches with large areas exposed to edge experienced lower nest success; these vegetation variables should be considered when using nest boxes to manage for Bewick's Wrens.

Effects of rotational grazing management on nesting greater sage‐grouse

ABSTRACTGrazing by domestic livestock is a ubiquitous land use in the sagebrush (Artemisia spp.) biome of western North America. Widespread, long‐term population declines in greater sage‐grouse (Centrocercus urophasianus) have elicited concern about potential negative effects of livestock management practices on sage‐grouse populations. We evaluated how recently implemented rotational grazing systems affected sage‐grouse nesting habitat quality as part of a large‐scale, replicated, natural experiment in central Montana, USA. We used Bayesian methods to assess support for effects of rotational grazing management and rest from grazing on daily survival rates of nearly 500 sage‐grouse nests monitored over 6 years, and mixed effects models to test for effects of rotational grazing and rest on vegetation structure. Though nests on rotationally grazed ranches displayed a trend toward greater daily survival rates, the evidence for an effect was weak. There was no evidence that rest from grazing (≥12 months) increased daily survival rates. Furthermore, rotational grazing systems and rest had negligible effects on herbaceous vegetation height and cover relative to other grazing strategies used in the study area. Results do not support the hypothesis that rotational grazing systems or rest from grazing increase nest success in the northern Great Plains. Estimated nest success, however, was comparable to range‐wide averages, suggesting concealing cover for nests is unlikely to be limiting growth of this population regardless of grazing strategy. In light of these results and recent research questioning reported relationships between grass height and nest survival, maximization of hiding cover may be overemphasized in grazing management guidelines and policies. Rather, our findings suggest a variety of locally appropriate grazing strategies focused on fundamental range health principles may provide adequate habitat quality for nesting sage‐grouse. © 2017 The Wildlife Society.

Multi-state, multi-stage modeling of nest-success suggests interaction between weather and land-use.

Many factors may affect daily nest survival. We present a novel multi-state, multi-stage model to estimate daily survival for each nest stage, daily hatching probability and probability that a failed nest died during a specific stage when stage of failure is unknown. The model does not require that hatching date be known. We used data from a large citizen science dataset to demonstrate the application of this approach, exploring the impact of laying dates, weather conditions, conserved soil moisture, soil carbon, habitat type and urbanization on failure rates of common blackbird (Turdus merula) nests. Models selected and estimates of nest success were similar to those of the simpler logistic exposure method, but accounted for additional uncertainty. Simulations suggest the multi-state approach performs better when incubation mortality is affected by nest age, but not when incubation mortality is assumed constant. Both approaches worked best when date of incubation initiation was known for all nests first visited during the incubation stage. Daily blackbird survival probabilities were higher in human rural habitat than in urban or countryside habitats supporting the hypothesis that these intermediate habitats offer a better balance between low food availability in urban areas and high predation rates in the wider countryside. Nest success was influenced more by recent precipitation in urban habitats, but by a longer-term measure of water availability, soil moisture, in non-human dominated habitats, indicating that climatic change is likely to alter relationships between habitat and breeding success (and their temporal scale) by influencing the trade-off between food availability and predation rates. The multi-state, multi-stage model developed here may be helpful to other researchers modelling ecological processes in which transition probabilities between multiple stages are of interest.

Does best‐practice crow Corvus corone and magpie Pica pica control on UK farmland improve nest success in hedgerow‐nesting songbirds? A field experiment

The role of predation by corvids on the breeding output of songbirds is unclear. Using a randomised‐pair design, we measured how nest success of hedgerow‐nesting passerines responded to the experimental removal of carrion crows and magpies. We worked in southern England at 32 paired sites around 4 km2 each, one with and one without best‐practice corvid control, studying four different pairs per year for four years 2011–2014. We counted corvids, and using songbird territory mapping and fledged brood counts without finding nests along transects, we estimated nest success as a brood/ territory ratio for the community of songbirds in 4 km of hedgerow at each site. Crows and magpies were still present at most removal sites but numbers were half as high as at paired non‐removal sites. Eighteen songbird species were frequently encountered at most sites with on average (±1 SD) 102 ± 30 territories per site. Using a generalised linear mixed model analysis the songbird community as a whole bred less well in treatment sites without corvid removal and in years with more rainfall. Nest success was down by 10% in non‐removal sites on average relative to removal sites over the four years. Excluding 2012 data because of exceptionally high spring rainfall that year, nest success was down 16% in the non‐removal sites on average in the other three years. For open‐cup nesting species as a group there was no difference in nest success between site types. Our data on hole nesters suggest that they were affected by treatment and contributed to our overall result. For species whose numbers are regulated through territoriality, nest‐site or habitat availability, spring abundance is unlikely to be affected by a 15% increase in breeding output. For species limited by nest success, it may be more important.

Effects of Micro-Habitat, Macro-Habitat, and Predator Space-Use on Success of Northern Bobwhite Nests (Poster Abstract)

Northern bobwhite (Colinus virginianus) exhibit high reproductive potential allowing populations to rapidly respond to newly created habitat and recover from high annual mortality. However, they experience low individual nest success, ranging from 16–50%. Survival of nests, particularly first nests, is an important demographic parameter that influences overall population performance and participation in alternative reproductive strategies such as renesting, double-clutching, and male-incubation. As bobwhite populations continue to decline, old paradigms regarding the relationships among habitat characteristics, predator abundance, and bobwhite productivity are being reexamined. A new emerging paradigm hypothesizes that habitat structure, landscape context, and predator context interact in a complex manner to influence fate of individual nests. Vegetation characteristics at nest sites, and components of bobwhite nesting habitat have been described, but few studies have shown relationships between vegetation characteristics and nest success. In contrast, several studies have demonstrated relationships between landscape structure and nest success, and ongoing research in the southeastern United States is demonstrating relationships between predator context and productivity. Although numerous studies have estimated nest success, no study has simultaneously examined effects of vegetation structure, landscape structure, and predator context on survival of bobwhite nests. We use incubated nests (n = 104) of radiomarked bobwhite on a managed area in east-central Mississippi from 1996–00 to examine effects of micro-habitat, macro-habitat, and predator space-use on nest survival. At each nest we characterized microhabitat by measuring vegetation height, density (Robel Visual Obstruction Reading), grass canopy coverage, forb canopy coverage, litter coverage, litter depth, and % bare ground. Within 50-, 200-, and 400-m concentric circles around nest sites we characterized landscape context using measures of patch richness, patch diversity, and interspersion/juxtaposition indices, and habitat specific measures of patch density, patch shape index, edge density, and % of landscape. We used year-specific harmonic mean utilization distributions of radiomarked raccoons to construct cumulative raccoon utilization distributions to measure intensity of space use by an important bobwhite nest predator. We used logistic regression on nest fate (hatched/failed) to develop predictive models of nest success as a function of micro-habitat, macro-habitat, and predator space-use. We constructed a set of candidate models that hypothesized nest fate as a function of micro-habitat, macro-habitat, predator space-use, micro and macro habitat, microhabitat and predator space use, macrohabitat and predator space use, and a global model that included all 3 groups of predictor variables. We used information theoretic approaches for model selection and inference.

Population vital rates of resident and translocated female greater sage‐grouse

ABSTRACTTranslocations have been recommended to reestablish, augment, and sustain genetic diversity in declining wildlife populations, including greater sage‐grouse (Centrocercus urophasianus; sage‐grouse). Characteristics of successful sage‐grouse translocations include suitable contiguous sagebrush (Artemisia spp.), seasonal habitats surrounded by geomorphic barriers, a residual resident population, and pre‐nesting releases. From 2009 to 2010, we studied vital rates of 60 translocated and 15 resident radio‐marked female sage‐grouse and their broods on Anthro Mountain, in the Ashley National Forest, northeastern Utah, USA to determine whether translocations could augment a declining meta‐population that inhabited suitable breeding habitats in a small spatially isolated landscape. Survival rates, and nest and brood success estimates for the resident and translocated sage‐grouse we studied were lower than reported range‐wide averages. Nest success was similar for resident and translocated birds (survival estimate: 0.468, 95% CI = 0.288–0.648) and we calculated weak, yet positive relationships to grass height and grass cover. Daily survival rates for chicks 0–19 days of age for resident females in 2009 (0.904, CI = 0.875–0.940) and in 2010 (0.910, CI = 0.888–0.945) were higher than for chicks raised by translocated females (0.883, CI = 0.850–0.915; 0.892, CI = 0.856–0.936, respectively), although differences were small and all 95% confidence intervals had substantial overlap. In 2009 and 2010, daily survival rates for chick 20–50 days of age were slightly higher for chicks reared by resident females (0.980, CI = 0.963–0.994; 0.998, CI = 0.978–1.000, respectively) than chicks reared by translocated females (0.877, CI = 0.623–0.959; 0.988, CI = 0.945–0.993, respectively). Chick survival for both groups was weakly correlated with grass cover. Although most translocated birds remained on the study area (82%), the low overall survival rates we report indicate that managers need to consider factors affecting survival of adult females, nests, and chicks when planning future translocations to augment sage‐grouse meta‐populations that occupy spatially isolated and space‐limited habitats. © 2016 The Wildlife Society.

Microhabitat Conditions in Wyoming's Sage-Grouse Core Areas: Effects on Nest Site Selection and Success.

The purpose of our study was to identify microhabitat characteristics of greater sage-grouse (Centrocercus urophasianus) nest site selection and survival to determine the quality of sage-grouse habitat in 5 regions of central and southwest Wyoming associated with Wyoming’s Core Area Policy. Wyoming’s Core Area Policy was enacted in 2008 to reduce human disturbance near the greatest densities of sage-grouse. Our analyses aimed to assess sage-grouse nest selection and success at multiple micro-spatial scales. We obtained microhabitat data from 928 sage-grouse nest locations and 819 random microhabitat locations from 2008–2014. Nest success was estimated from 924 nests with survival data. Sage-grouse selected nests with greater sagebrush cover and height, visual obstruction, and number of small gaps between shrubs (gap size ≥0.5 m and <1.0 m), while selecting for less bare ground and rock. With the exception of more small gaps between shrubs, we did not find any differences in availability of these microhabitat characteristics between locations within and outside of Core Areas. In addition, we found little supporting evidence that sage-grouse were selecting different nest sites in Core Areas relative to areas outside of Core. The Kaplan-Meier nest success estimate for a 27-day incubation period was 42.0% (95% CI: 38.4–45.9%). Risk of nest failure was negatively associated with greater rock and more medium-sized gaps between shrubs (gap size ≥2.0 m and <3.0 m). Within our study areas, Wyoming’s Core Areas did not have differing microhabitat quality compared to outside of Core Areas. The close proximity of our locations within and outside of Core Areas likely explained our lack of finding differences in microhabitat quality among locations within these landscapes. However, the Core Area Policy is most likely to conserve high quality habitat at larger spatial scales, which over decades may have cascading effects on microhabitat quality available between areas within and outside of Core Areas.

Striped-tailed Yellow-finch nesting success in abandoned mining pits from central Brazilian cerrado.

Suitability of degraded areas as breeding habitats can be tested through assessment of nest predation rates. In this study we estimated nest success in relation to several potential predictors of nest survival in the Stripe-tailed Yellow-finch (Sicalis citrina) breeding in abandoned mining pits at Brasília National Park. We monitored 73 nests during the 2007-breeding season. Predation was the main cause of nest failure (n = 48, 66%); while six nests were abandoned (8%) and 19 nests produced young (26%). Mayfield's daily survival rates and nest success were 0.94 and 23%, respectively. Our results from nest survival models on program MARK indicated that daily survival rates increase linearly towards the end of the breeding season and decrease as nests aged. None of the nest individual covariates we tested - nest height, nest size, nest substrate, and edge effect - were important predictors of nest survival; however, nests placed on the most common plant tended to have higher survival probabilities. Also, there was no observer effect on daily survival rates. Our study suggests that abandoned mining pits may be suitable alternative breeding habitats for Striped-tailed Yellow-finches since nest survival rates were similar to other studies in the central cerrado region.

Success and Predation of Bird Nests in Grasslands at Valley Forge National Historical Park

Abstract Populations of grassland birds are declining in the Northeast due to habitat loss and fragmentation. Fragmentation of grasslands can contribute to lower breeding success of grassland birds by altering local predator communities. Using miniature video cameras, I estimated nest success and identified nest predators in grassland fragments at Valley Forge National Historical Park in southeastern Pennsylvania. Estimated nest-success probability for Sturnella magna (Eastern Meadowlark) at Valley Forge was 0.25 (0.04–0.65, n = 7) and similar to estimates from the Midwest, but slightly lower than other studies in the Northeast. Nest success for Spizella pusilla (Field Sparrow; 0.77 [0.31–0.98, n = 8]) and Agelaius phoeniceus (Red-winged Blackbird; 0.48 [0.18–0.80, n = 10]) was higher than estimates from other studies. The local predator community identified at Valley Forge was less diverse than documented in other studies, with only 4 species depredating 8 of 25 monitored nests. The primary predator was ...

Estimating Raptor Nesting Success: Old and New Approaches.

Studies of nesting success can be valuable in assessing the status of raptor populations, but differing monitoring protocols can present unique challenges when comparing populations of different species across time or geographic areas. We used large datasets from long-term studies of 3 raptor species to compare estimates of apparent nest success (ANS, the ratio of successful to total number of nesting attempts), Mayfield nesting success, and the logistic-exposure model of nest survival. Golden eagles (Aquila chrysaetos), prairie falcons (Falco mexicanus), and American kestrels (F. sparverius) differ in their breeding biology and the methods often used to monitor their reproduction. Mayfield and logistic-exposure models generated similar estimates of nesting success with similar levels of precision. Apparent nest success overestimated nesting success and was particularly sensitive to inclusion of nesting attempts discovered late in the nesting season. Thus, the ANS estimator is inappropriate when exact point estimates are required, especially when most raptor pairs cannot be located before or soon after laying eggs. However, ANS may be sufficient to assess long-term trends of species in which nesting attempts are highly detectable.

Testing common assumptions in studies of songbird nest success

We studied Ovenbird Seiurus aurocapilla and Golden-winged Warbler Vermivorachrysoptera populations in northern Minnesota, USA, to test two common assumptions instudies of songbird nest success: (1) that the condition of an empty nest on or near itsexpected fledge date is an indicator of nest fate; and (2) that the presence of a fledgling orfamily group within a territory confirms a successful nest in that territory. We monitoredthe condition of nests and used radiotelemetry to monitor juveniles through the expectedfledging date and early post-fledging period. Of nests that contained nestlings 1–2 daysbefore the expected fledge date, fates were misidentified using nest condition alone for9.5% of Ovenbird nests, but those misidentifications were made in both directions (suc-ceeded or failed), yielding only a small bias in estimated nest success. However, 20% ofGolden-winged Warbler nests were misidentified as successful using nest condition duringthe final visit interval, biasing the nest success estimate upward by 21–28% depending onthe treatment of uncertain nest fates. Fledgling Ovenbirds from 58% of nests travelledbeyond their natal territory within 24 h, rising to 98% after 5 days, and those fledglingstravelled up to 390 m from nests within 10 days of fledging. Fledgling Golden-wingedWarblers from 13% of nests travelled beyond their natal territory within 24 h, rising to85% after 5 days, and those fledglings travelled up to 510 m from nests within 10 days offledging. We conclude that nest condition and fledgling presence can be misleading indica-tors of nest fate, probably commonly biasing nest success estimates upward, and we rec-ommend that these assumptions should be tested in additional species.Keywords: fledgling, Golden-winged Warbler, Ovenbird, Seiurus aurocapilla, telemetry,Vermivora chrysoptera.Estimates of songbird reproductive success, typi-cally limited to nest data, are used to assess habitatquality (e.g. Weinberg & Roth 1998), model pop-ulation dynamics (e.g. Podolski et al. 2007), iden-tify source and sink populations (e.g. Donovan etal. 1995), and inform conservation and manage-ment plans (e.g. Woodworth 1999). Althoughsongbird population growth may be generally moresensitive to adult annual survival and fledgling sur-vival (Donovan & Thompson 2001, Streby &Andersen 2011), population growth is also sensi-tive to variation in nest success (Donovan et al.1995), and nest success is the only directly esti-mated parameter in most studies of songbirdreproductive success (Anders et al. 1997). Manypopulation models account for re-nesting (birdsnesting again after initial failure) and estimates ofnest productivity (number of young produced persuccessful nest). All such studies require accuratefield identification of whether each monitored nestsucceeded or failed in producing young. However,observational studies of songbird nests often

Nesting ecology of Florida mottled ducks using altered habitats

Habitat loss has negatively affected many species of upland-nesting waterfowl. Very few areas contain pristine nesting habitat in Florida because of conversion to agriculture and urban development. Although some species have acclimated to nesting in an altered landscape, little is known about the nesting ecology of Florida mottled ducks (Anas fulvigula fulvigula) that use altered habitats. We located and monitored 77 nests of radio-marked Florida mottled ducks in the Upper St. Johns River Basin (1999–2002) and in south Florida (2009–2011) and tested the effects of nest vegetation characteristics, human disturbance, and temporal variables on estimates of daily nest survival. We also calculated the percent of females that nested each year as a measure of breeding propensity. Nest age at discovery had a positive relationship with daily nest survival. Daily nest survival rates did not vary within or among years and were unaffected by density and height of vegetation at the nest and human disturbance parameters we measured. Breeding propensity ranged from 25% to 56%. Breeding propensities were less than those of other duck species, but our nest success estimate of 28% was greater than most estimates for ducks and is not likely to limit population growth of Florida mottled ducks. © 2013 The Wildlife Society.

Nesting Ecology of Swainson's Warblers in a South Carolina Bottomland Forest

Abstract We studied the nesting ecology of Swainson's Warblers (Limnothylpis swainsonii) in Britton's Neck, South Carolina, USA and found 144 nests of which 78 were active. Nest initiations followed a bimodal distribution. Clutches averaged (± SE) 3.19 ± 0.20 eggs and 2.50 ± 0.33 fledglings per nest. The Mayfield nest success estimate for a 23-day cycle was 50%. Logistic exposure models indicate nest success to be most impacted by Brown-headed Cowbird (Molothrus ater) nest parasitism, nest age, and distance to the nearest swamp. Unparasitized nests that were younger in age and further from a swamp had the highest daily survival rates. Ten percent of nests were parasitized by Brown-headed Cowbirds with a 26% reduction in Swainson's Warbler hatching and an 89% reduction in fledgling production. Multiple brooding was observed in 21% of 2000 and 2001 Swainson's Warbler nests. Vines, such as greenbrier (Smilax spp.), were the most common substrate used for nesting, although two-thirds of the nests contained ca...

Nest success and hatchling survival of American alligators within inland wetlands of east Texas

AbstractBecause of liberalization of American alligator (Alligator mississippiensis) harvest management in Texas, estimates of nest success and hatchling survival for inland populations are essential for long‐term, sustainable population and harvest management. To date, few studies have examined American alligator nest success and hatchling survival. We initiated a 3‐year study from 2006 to 2008 to document alligator nest success and hatchling survival within several wetlands in east Texas. From June 2006 to August 2008, we located 30 nests from 3 wetlands within east Texas, where overall nest success was 44.2% (95% CI = 25.1–63.1%), irrespective of year. Nest circumference and day during the nesting season exerted the greatest influence on nest success. Additionally, from August 2006 to August 2008 we captured, marked, and released 271 hatchling alligators at Little Sandy National Wildlife Refuge, and recaptured an additional 192 hatchling alligators during this time. We estimated yearly apparent survival at 6.0% (95% CI = 2.0–14.6%) for hatchling alligators born in 2006 and 43.0% (95% CI = 28.4–57.8%) for those hatched in 2007. Variation in nest success and hatchling survival was likely attributed to fluctuating water levels and habitat management practices. Alligator harvest regulations need to account for variability in nest success and hatchling survival by including site‐specific estimates of these metrics into harvest models. Failing to account for spatial and temporal variation in nest success and hatchling survival may result in unsustainable harvest and/or overharvest. © 2012 The Wildlife Society.

Nest survival of piping plovers at a dynamic reservoir indicates an ecological trap for a threatened population

In the past 60years, reservoirs have reshaped riverine ecosystems and transformed breeding habitats used by the threatened piping plover (Charadrius melodus; hereafter plover). Currently, 29% of the Northern Great Plains plover population nests at reservoirs that might function as ecological traps because reservoirs have more diverse habitat features and greater dynamics in water levels than habitats historically used by breeding plovers. We examined factors influencing daily survival rates (DSR) of 346 plover nests at Lake Sakakawea (SAK; reservoir) during 2006-2009 by evaluating multiple a priori models, and we used our best model to hindcast nest success of plovers during 1985-2009. Our observed and hindcast estimates of nest success were low compared to published estimates. Previous findings indicate that plovers prefer nest sites that are low relative to water level. We found that elevation of nests above the water level had a strong positive correlation with DSR because water levels of SAK typically increased throughout the nesting period. Habitat characteristics on the reservoir differ from those that shaped nest-site selection for plovers. Accordingly, extraordinary nest loss occurs there in many years, largely due to inundation of nests, and based on low fledging rates those losses were not compensated by potential changes in chick survival. Therefore, our example supports the concept of ecological traps in birds because it addresses quantitative assessments of habitat preference and productivity over 25years (since species listing) and affects a large portion of the population.

No evidence for observer effects on Lark Sparrow nest survival

ABSTRACT Methods for monitoring bird nests might influence rates of nest predation, but the effects of various methods (e.g., visual markers and observer visitation rates) are often separately investigated among disparate avian taxa and geographic regions. Few investigators have explored the potential effects observers might have on nest success of grassland birds, despite concerns regarding population declines of these species in North America. We examined the possible effects of three monitoring techniques on daily nest survival of Lark Sparrows (Chondestes grammacus): (1) presence or absence of visible markers near nests, (2) observer visitation frequency, and (3) presence or absence of data loggers in nests. We monitored 113 Lark Sparrow nests during the 2009 breeding season. Of these nests, 88.5% failed due to predation, abandonment, weather, or unknown causes, yielding an overall nest success estimate of 9.8% based on daily survival estimation. Main effects of each monitoring technique appeared in top (ΔAICc <2) logistic exposure models. However, 95% confidence intervals around parameter estimates for each technique included zero, indicating no significant effects on daily nest survival. Our results suggest that the nest-monitoring techniques we used had no effect on Lark Sparrow nest success and, if true, nest survival of other songbirds in arid grasslands of the Great Plains may also be unaffected by cautious nest monitoring. However, we cannot rule out the possibility that any effects of the various techniques in our study were masked by locally intense nest predation. Therefore, additional study is needed to determine if there may be observable variation in nest survival among various nest-monitoring treatments in other areas of the southern Great Plains where nest predation is less frequent. Los métodos para monitorear los nidos de aves pueden influir en la tasa de depredación, pero el efecto de varios métodos (ej. marcadores visuales, tasa de visita del observador a los nidos) usualmente se investiga por separado entre los diferentes taxones de aves y regiones geográficas. Pocas investigaciones han explorado los efectos potenciales que los observadores puedan tener en el éxito de anidamiento de aves de hierbazales, pese a preocupaciones relacionadas con la reducción de estos en Norte América. Examinamos los posibles efectos de tres técnicas de monitoreo en la sobrevivencia diaria de individuos de Chondestes grammacus: (1) presencia o ausencia de marcadores visuales cerca de los nidos, (2) la frecuencia de visitas por observadores y (3) la presencia o ausencia de recopiladores electrónicos de datos en los nidos. Monitoreamos 113 nidos de Chondestes durante la temporada reproductiva del 2009. De estos nidos el 88.5% fracasaron debido a depredación, abandono del nido, las inclemencias del tiempo, o causas desconocidas, arrojando un éxito de anidamiento estimado en 9.8%, basado en un estimado de supervivencia diaria. El efecto principal de cada técnica de monitoreo apareció en el tope de un modelo de exposición logística (ΔAICc <2). Sin embargo, el intervalo de confianza de 95% sobre los parámetros estimados para cada técnica incluyo el cero, lo que indica que no hubo un efecto significativo en la sobrevivencia diaria de los nidos. Nuestros resultados sugieren que las técnicas de monitoreo de nidos que utilizamos no tuvieron efecto en el éxito de anidamiento de las aves. Si esto es correcto, la sobrevivencia de nidos de aves canoras en hierbazales áridos de las Grandes Planicies, pudiera también ser inafectada por el monitoreo cuidadoso. Sin embargo, no podemos dejar fuera la posibilidad de que algún efecto del monitoreo haya quedado opacado por la alta depredación. Por lo tanto, se necesitan estudios adicionales para determinar si hay variaciones observables en la sobrevivencia de nidos entre diferentes formas de monitoreo en otras áreas de las Grandes Planicies en donde la depredación no sea tan frecuente.